1. Technical Field
The present invention relates to a piezoelectric material used in piezoelectric elements, or the like mounted in various devices such as actuators, ultrasonic devices such as ultrasonic oscillators, ultrasonic motors, pressure sensors, and pyroelectric elements such as IR sensors, a piezoelectric element using the material, a liquid ejecting head, a liquid ejecting apparatus, an ultrasonic sensor, a piezoelectric motor, and a power generator.
2. Related Art
A piezoelectric material, which is used as a piezoelectric layer (piezoelectric ceramics) constituting a piezoelectric element, or the like mounted in various devices such as actuators, ultrasonic devices such as ultrasonic oscillators, ultrasonic motors, pressure sensors, and pyroelectric elements such as IR sensors is required to have a remarkable piezoelectric characteristic, and as a representative example thereof, lead zirconate titanate (PZT) is exemplified.
However, from an environmental sensitivity point of view, a piezoelectric material whose lead content is suppressed is desired. As such a lead-free piezoelectric material, there are a piezoelectric material that includes an alkali metal such as KxNa(1-x)NbO3, and (Ba, Na)TiO3, a piezoelectric material such as BiFeO3—BaTiO3, and the like.
With regard to such a piezoelectric material, it is known that a remarkable piezoelectric characteristic can be obtained by using a composition near a Morphotropic Phase Boundary (MPB). However, in a phase diagram that employs compositions for the horizontal axis and temperatures for the vertical axis, the MPB line of PZT is substantially parallel to the temperature axis or positioned vertical to the composition axis, but an MPB line of a lead-free piezoelectric material is generally inclined with respect to the temperature axis (for example, refer to FIG. 1 of JP-A-2009-215111, or the like). When the MPB line is inclined as described above, even if a composition positioned on the MPB line at a specific temperature, for example, room temperature according to a desired characteristic is selected, it is set away from the MPB line on the composition-temperature state diagram when the environmental temperature changes, and thus, there is a problem in that there is a temperature area in which a piezoelectric characteristic, and dielectric characteristic of an element deteriorates due to changes in environmental temperature, generation of heat during usage, or the like.
Thus, from a desire that the MPB line is erect if possible in the phase diagram described above and a desire that a piezoelectric material has a remarkable piezoelectric characteristic and dielectric characteristic at around a normal temperature (room temperature) and can be used even at a temperature as high as possible, a piezoelectric material that has Curie temperature (Tc) as high as it can be, which is generally inversely proportional to the piezoelectric characteristic, has been demanded.
For this reason, technologies for improving temperature dependency by laminating a plurality of piezoelectric materials having different compositions have been proposed (refer to JP-A-2003-277143 and JPA-2011-181764), but the fact that the plurality of different piezoelectric materials should be used is a problem.
As described above, currently, there is no lead-free piezoelectric material compared to PZT, and thus, introduction of a lead-free piezoelectric material having a remarkable piezoelectric characteristic and dielectric characteristic in a wide use environment temperature range and having a high Curie temperature has been greatly desired.
Note that such a problem also arises not only in ink jet-type recording heads but also in other liquid ejecting heads that discharge droplets other than ink, and also arises even in piezoelectric elements used in devices other than such liquid ejecting heads.